Packaging Methods And Packaging Matreials For Fine Powders

ABSTRACT

A method for treating a package. In the method a first plastic film sack ( 14 ) is provided, that has a flexible wall ( 18 ) comprising a plastic film ( 3 ), the wall ( 18 ) having an outer surface ( 5 ). A second plastic film sack is provided. A product of powder form is provided that has an upper size limit which is the particle size smaller than 1 mass-percent of the particles of the product of powder form, which upper size limit is at most 5000 microns and a lower size limit which is the particle size bigger than 1 mass-percent of the particles of the product of powder form. The product of powder form is packed in the first plastic film sack ( 14 ), and the first plastic film sack is, at least partly, placed upon the second plastic film sack. According to the invention, such a first plastic film sack is provided in which at least a part of the outer surface ( 5 ) of the flexible wall ( 18 ), the roughened surface-part ( 6 ), comprises antislip protrusions ( 7 ) which antislip protrusions ( 7 ) are constituted by roughening particles, of polymer material, fixed to the outer surface ( 5 ) and the height ( 8 ), above the outer surface ( 5 ) of the plastic film wall, of at least a part of the antislip protrusions ( 7 ) is bigger than the lower size limit of the product of powder form.

TECHNICAL FIELD

The invention relates to skidproof plastic film packaging means andtheir use for packaging products comprising fine powders.

BACKGROUND OF THE INVENTION

In the industry, bulk solid powder products, comprising fine granules,are in big quantities packed up in sacks of 5 to 50 kilograms. Examplesof products of that kind are cement, the so-called dry-mixes includingcement or lime powder (e.g. dry-mortar, dry concrete-mix),limestone-powder, lime-hydrate powder, polymer powders (e.g. suspensionpoly-vinylchloride, S-PVC) etc. For the bagging of these products,easily mixing with air, typically paper sacks of porous walls,particularly valve bags, are used. It would be cheaper to use plasticpackaging film for the automatic bagging of the fine powders, e.g.cement mixes. That can be done, for example, with the packaging machinecalled “Compacta for Cement”, made by Italian company “BL Bagline”,representing the state of the art. Still, the packaging of fine powdersinto plastic sacks has not become widespread. We have found that one,maybe the most important, reason thereof is that if fine granulatedproducts are packed in traditional plastic film bags, then the stabilityof the stacks built from the bags is insufficient, the bags slip apart.That is, on the one hand, caused by the coefficient of friction of thesmooth surface of the ordinary plastic film being generally lower thanthat of the usual paper grades, especially if the film is polluted withfine dust. On the other hand, the wall of the plastic film bag, unlikethat of a paper bag, is not porous. Therefore a certain airing can atmost be provided with perforating the surface of the film, during thefilling-in of the powder-air mixture. A relatively fast airing canusually be achieved with vent hole perforations of at least about 3 to 4mm's, but even that is less than sufficient. Because of the insufficientairing, the bags remain “inflated”, containing surplus air, even whenthey get into, and become a part of, a stack of bags. There are aircushions left in the inflated bags lying upon each other which, in thecase of plastic films used so far for this purpose, makes the stackunacceptably unstable and the bags slip up on each other and fall fromthe pallet. All that prevents inexpensive plastic packaging films frombeing used with products of fine granules.

There has traditionally been an endeavour to decrease the slip ofplastic bags by increasing the coefficient of friction of the film ofthe bags. Therefore, in accordance with the solution of the companyNordenia Kunststoffe, published in document DE 3437414A1, the wall ofthe plastic bag has been strongly embossed, from inside out, thusforming in the film hollow protrusions protruding to the outside. Therehas been an endeavour to form high and sharp protrusions by embossingthe film which, however, weakens the film. According to our ownmeasurements, such a strong embossing may decrease the breaking strengthof the film by up to 14.5%, which increases the danger of the burstingof the inflated bag being in the stack. Therefore we deem embossing adisadvantageous solution in this field of packaging. At the same time,however, in a heavily dusty environment the beneficial effects of theembossing to the coefficient of friction of the film are negligible. Thecoefficient of friction of plastic films easy to emboss, rich in speciallow density polyethylenes, is usually low anyway. In addition, thehollow embossing, under the heavy load of the cement bags, will soonflatten out and get planar.

It is, on the other hand, known that U.S. Pat. No. 6,444,080,originating from the present applicants, is related to plastic films, ofdecreased slip, for making sacks between which the clinging is notprimarily provided by the usual static coefficient of friction. In thatsolution at least one of the sliding film surfaces is rough, and itsroughening protrusions interact with an engaging element of a loose,fibrous structure, practicably with an inexpensive nonwoven fabric, in away by which a bond, of a strong shear strength, can be provided betweenthe engaging element and the rough film or films. The essence therein isthat the antislip protrusions are capable of penetrating between thefree filaments, therefore the adhesion is not only based on thecoefficient of friction of the materials but rather on a kind of amechanical lock effect. According to the document (and to our ownexperience) the adhesion can be further increased if the antislipprotrusions are undercut, i.e., their projection to the surface of thefilm is bigger than their intersection with the plane of the film.

This kind of film-roughening has, over other kinds of film rougheningmethods, the distinguishing feature that the roughening protrusions areformed with fixing powder granules or other, essentially point-like,particles to the film and preferably have a typical undercut. Thus theseprotrusions are not mere embossed protrusions but they add extramaterial to the film therefore they do not essentially weaken the film.These protrusions are thus of essentially point-like topology incomparison with the protrusions of such other kinds of roughening inwhich the protrusions are long, straight lines or ridges and valleys oflinear topology, winding in a random manner.

In our experience the aforementioned antislip solution, comprising roughfilm and engaging element, has worked very well and reliably in practicewith skidproof packaging of pellets, and it can be used in several ways.In one possible solution at least the upper surfaces of the sacks, laidupon each other, are rough and at least their lower surfaces areprovided with an engaging element, for example a nonwoven fabric, fixedthereto (the roles of the upper and lower surfaces can be inverted). Theengaging element can be fixed to the sacks before, during or after thefilling. Here the sacks must be stacked in a brick-like bond. In anothersolution both the lower and upper surfaces of the bags are rough, andthe engaging element, for example nonwoven fabric, is present in theform of a stick-sheet laid between the layers of bags. The latterarrangement provides the advantage that the bags do not have to bestacked in a brick-bond pattern but they can also be arranged in columnsand that in many cases it is not necessary to apply an engaging sheet toevery layer (source reduction). It is a further advantage of the latterarrangement that the different polymer materials of the system (nonwovenfabric and bags) can easily be separated with a view to a recycling.

The requirement of a good printability of the rough sack surface promptsthe skilled person to use antislip protrusions as small and as low aspossible. The same urge originates from a further advantage of the lowerprotrusions, that the surface of such bags is more comfortable to touch,is not so rough, which is very important for many smaller industrialusers (for those whose workers move the bags by hand and a too abrasiverough film surface might hurt their skin).

That method or such film bags are not known, from the prior art, to beused in the field of packaging fine powder products.

DISCLOSURE OF THE INVENTION

Our main objective is to provide solutions (packaging methods, packagesand packaging means) that make it possible to use the more economicalplastic film packaging with fine powdery products with security. Ourparticular objective is to combine the non-slip system, comprising roughfilm and fibrous engaging element, with the packaging of fine powders insuch new ways which particular combinations provide surprising,advantageous results and unexpected effects.

We have discovered that the roughened plastic sacks provided withengaging elements in accordance with the aforementioned U.S. Pat. No.6,444,080 patent provide, in case of favourable circumstances, so strongskidproofing even in a dusty, contaminated state which even makes stackscomprising inflated bags completely safe. We, however, have recognisedthat in order of our objective, the rough film must fulfill furtherspecial criteria if applied with fine powders. The thing is that the“rough film and engaging element” system, working reliably undercircumstances free of fine powders (e.g., at the packaging of pellets),will, in the presence of fine powders, sometimes work perfectly but may,at other times, go wrong unexpectedly and unnoticed.

The fine powder, constituting the contents, may, during the packaging,e.g., during or after the filling of the packages, or during thestacking or during a successive transportation, get to the outer, roughside of the packaging film, either from the ambient air or from thefilled sack, through its airing orifices. That, depending on conditionsnot published so far, influences, apparently unpredictably, theengagement between the rough film surface and the engaging element andthereby the stability of the stack. In unfavourable circumstances thedust, being on the outer, rough surface of the bag, may fill the spacebetween the protrusions and impede the engaging fibres penetrating andhooking there. That may make the quality of the skidproofingunpredictable, unreliable and dependent on time. As we have recognised,the, otherwise excellent, skidproofing effect provided by the antislipprotrusions and the fibrous engaging element can deteriorate if theprotrusions applied are too low as compared to the size of the granulesof the dust getting to the rough outer surface of the film. If, however,the protrusions are sufficiently high, the skidproofing will reliably besustained.

Under a certain particle size, in case of fine powders, at fillingpowdery products into plastic sacks there is a risk of the relativelysmallest particles of the powder, belonging to its finest fraction,flying away and mixing with the ambient air. In order that not too muchpowder escapes, the filling is usually done with suitable care (e.g.,with a filling spout moved during the filling from the bottom of the bagtoward its top) and suitably slowly. That, in practice, will mean thatthe bags are filled at a speed at which a part of just the smallestpowder particles fly away in the ambient air. For example, during thefilling of valve bags the fine powder will escape next to the valvewhile with form-fill-seal (FFS) machines some fine powder puffs out atthe open mouth of the bag. All that does not depend on whether the wallof the bag is perforated, breathing, or not. In unfavourablecircumstances, the fine dust settling from the air, during or after thepackaging, onto the bags, being just filled or already filled, can fillthe space between the protrusions and can make it difficult for theengaging fibres to enter there. That makes the quality of theskidproofing unreliable and dependent on time.

It is, even with highly automated packaging, common that the process ofpackaging and stacking is interrupted, for some reasons, for some time(e.g., for some minutes or even for several hours). In that case thetime, elapsed till two packages, to be put on top of each other, areactually laid on each other, is lengthened and during that time somewhatmore airborne dust settles, from the ambient air, to the lower packagethan usual. In unfortunate circumstances that can lead to the antislipeffect, between the two packages, disappearing unnoticed and completely.That creates a sneaking, slippery abutment inside the stack, between itstwo neighbouring layers, one being above the other, which of courseendangers the security of the whole stack. That phenomenon is surprisingbecause the filled packages, of apparently dusty surface, put on top ofeach other with the usual time period stick to each other perfectly, butthe special, fine-powdery circumstances involve a surprising andunexpected time-factor into the behaviour of the product, making thesame dependent on time, whose considering is not obvious for the skilledperson.

The slip-preventing effect provided by the antislip protrusions and thefibrous engaging element can deteriorate if the protrusions applied aretoo low as compared to the size of the fine fraction of the powderfilled in. If, however, the protrusions are high enough, theskidproofing will be securely maintained.

The essence of our respective invention is a method for treating apackage, in which

-   -   a first plastic film sack is provided,        -   the first plastic film sack having a flexible wall            comprising a plastic film,            -   the wall having an outer surface,    -   a second plastic film sack is provided, and    -   a product of powder form is provided that has        -   an upper size limit which is the particle size smaller than            1 mass-percent of the particles of the product of powder            form, which upper size limit is at most 5000 microns and        -   a lower size limit which is the particle size bigger than 1            mass-percent of the particles of the product of powder form,    -   the product of powder form is packed in the first plastic film        sack, and    -   the first plastic film sack is, at least partly, placed upon the        second plastic film sack,

in which method, in accordance with the invention, such a first plasticfilm sack is provided in which at least a part of the outer surface ofthe flexible wall, the so-called roughened surface-part, comprisesantislip protrusions which antislip protrusions are constituted byroughening particles (preferably granules), of polymer material, fixedto the outer surface and the height, above the outer surface of theplastic film wall, of at least a part of the antislip protrusions isbigger than the lower size limit of the product of powder form.

The first plastic film sack can be a pillow sack, a side gusseted sack,a valve sack or any suitable sack. Its substance is typicallypolyolefine, e.g., polyethylene, but can also be something else. Theplastic film of the sack can comprise one layer or multiple layers. Itcan also be the case that the plastic film of the sack is a materialwoven from strips slit from single- or multilayer films during themanufacture of which the film, made with extrusion, is slit into narrowstrips and a fabric is made from the strips, for example with circularweaving or flat weaving. The sack can, for example, be welded and/oradhered and/or sewn. The second plastic film sack can be similar to ordifferent from the first one.

The size of a particle is its biggest extent. The product of powder formis packed in the first plastic film sack which means that it is filledinto the film sack (for example, with gravity force or with casting withimpulse or, mixed with air, with blowing etc.) and the film sack ispreferably suitably closed as necessary, for example its open mouth isclosed with welding or its filling valve is closed with laying down thesack. The surface part provided with antislip protrusions, the so-calledroughened surface part, can preferably decrease the slip interactingwith an engaging element of a fibrous structure, e.g., with a nonwovenfabric. The protrusions are solid and were made with fixing plasticparticles (e.g., plastic powder particles) to the outer surface. That,on the one hand, provides a suitable geometry, sticking out, of theprotrusion, while, on the other hand, makes it possible that thematerial of the particles and that of the film be different. Theroughening protrusions are preferably granules but the final shape ofthe protrusions may be different from a usual granule shape, it may bemore or less impressed, smeared, stretched etc., showing a result of themanufacturing process. The way of their fixation may be welding oradhering or any other suitable way. It is an essential element of theinvention that at least a part of the protrusions is higher than thelower size limit of the powdery contents. It is an advantage of themethod that it resists the harmful effect, cumulative in time andspoiling the skidproofing, of the fine dust settling from the air.

We have recognised that, in order of a very strong non-slip bond withthe fibres of the engaging element of a fibrous structure, it is furtherpreferable if the granules of the fine dust, potentially settling on theouter surface of the film between the antislip protrusions, are smallerthan the height, above the outer surface of the film, of the side edge,widest point, of the undercut antislip protrusion. In this case thefibres of the engaging element slip into the undercut of the protrusion,e.g., to the foot of the protruding granule, to the section line of thegranule and the film and get fixed there with a mechanical locking.Therefore it is preferable if in the aforementioned method such a firstplastic film sack is provided in which, in at least one vertical sectiontaken during a horizontal state of the outer surface, of at least a partof the antislip protrusions, one or both of the leftmost and rightmostpoints of the antislip protrusion are at a greater free distance fromthe outer surface than the lower size limit of the product of powderform. The benefit of the method is that this way a layer of the finepowder settling can not prevent the engaging fibres from hooking withthe lower, undercut portions of the protrusions.

It is, with respect to skidproofing, preferable if in the aforementionedmethods such a skidproofing material, of a suitable loose fibrousstructure and inherent strength (preferably a nonwoven fabric), isprovided, at least partly placed between the film sacks, which iscapable of a suitable nonslip bond with the antislip protrusions due toits containing the elementary filaments or yarns in such a density andlayer thickness at which a mechanical bond is formed between itselementary filaments or yarns and the antislip protrusions.

The point is that the antislip protrusions are able to penetrate betweenthe free fibres and that is how a solid mechanical bond, in shearingdirection, is formed. In order of an increased effective surfacialfriction it is preferable if both film sack walls, contacting each otherwith the mediation of the skidproofing material, are roughened, but ifthat can not be provided then it is preferable to fix the skidproofingmaterial to the non-roughed sack wall. In one practicable embodiment ofthe method the film sacks, roughened both on their upper and lower mainsurfaces, are stacked in multiple layers on a pallet, and one or more orevery boundary surface between the layers is filled, entirely or partly,with a skidproofing material of a suitable looseness and tear strength(preferably with a nonwoven fabric). That can, for example, be performedwith laying, right after placing the layers of sacks, on the top of therespective sacks a nonwoven fabric of a size approximately equal to thearea of the pallet.

The filled package, utilised in the aforementioned method, inherentlypossesses the advantages originating in the invention, because from suchpackages a stable stack can be built in several ways, with a suitableengaging element of fibrous structure (e.g., with stick-sheets offibrous structure, for example of nonwoven fabric, laid between thelayers of the stack).

Thus the essence of our respective invention is a package,

-   -   comprising a plastic film sack and a product of powder form        packed therein,    -   the plastic film sack having a flexible wall comprised of a        plastic film,        -   the wall having an outer surface,    -   the product of powder form having        -   an upper size limit which is the particle size smaller than            1 mass-percent of the particles of the product of powder            form, which upper size limit is at most 5000 microns and        -   a lower size limit which is the particle size bigger than 1            mass-percent of the particles of the product of powder form,

which package is, in accordance with the invention, such as at least apart of the outer surface of the flexible wall of its plastic film sack,the so-called roughened surface-part, comprises antislip protrusionswhich antislip protrusions are constituted by roughening particles(preferably granules), of polymer material, fixed to the outer surfaceand the height, above the outer surface of the plastic film wall, of atleast a part of the antislip protrusions is bigger than the lower sizelimit of the product of powder form.

The advantage of the package is that it resists the harmful effect,cumulative in time and spoiling the skidproofing, of the fine dustsettling from the air.

Analogously, it is preferable if the aforementioned package is such asin at least one vertical section taken during a horizontal state of theouter surface, of at least a part of the antislip protrusions of itsplastic film sack, one or both of the leftmost and rightmost points ofthe antislip protrusion are at a greater free distance from the outersurface than the lower size limit of the product of powder form. Thebenefit of such a package is that this way a layer of the fine powdersettling can not prevent the engaging fibres from hooking with thelower, undercut portions of the protrusions.

It is, with respect to skidproofing, preferable if the aforementionedpackage is such as it has a skidproofing material of a suitable loosefibrous structure and inherent strength (preferably a nonwoven fabric),placed suitably to the outer surface of its plastic film sack, which iscapable of a suitable nonslip bond with the antislip protrusions due toits containing the elementary filaments or yarns in such a density andlayer thickness at which a mechanical bond is formed between itselementary filaments or yarns and the antislip protrusions.

For a skilled person, the aforementioned U.S. Pat. No. 6,444,080 patentand our own comments added thereto hereinabove provide sufficientteaching as concerning a suitable placing and, in case of necessity,fixing of the skidproofing material as an engaging element. Theskidproofing material, capable of forming a mechanical bond, providesits beneficial, stabilising effect when the package is put into a stack,forming a mechanical bond with the antislip protrusions of packages,similar to and neighbouring with the package.

At places where such a product of powder form is packed in plastic sackswhich powder has a component of a size smaller than 3 microns, it is, inour experience, essentially almost impossible to prevent the very tinydust granules from unnoticedly escaping, rising in the air and latersettling to the surface of the sacks already filled. The very fine dustsettling on the surface of the sack, in a layer thicker and thicker bytime, will dramatically decrease the skidproofing between the antislipprotrusions and the fibrous engaging element after a certain time,because it fills the space between the protrusions and makes itdifficult for the engaging fibres to enter there. That makes the qualityof the skidproofing unreliable and dependent on time. That can beavoided with applying suitably high antislip protrusions. The essence ofour respective invention is a method for treating a package, in which

-   -   a first plastic film sack is provided,        -   the first plastic film sack having a flexible wall            comprising a plastic film,            -   the wall having an outer surface,    -   a second plastic film sack is provided, and    -   a product of powder form is provided that comprises, at least        partly, particles smaller than 3 microns,    -   the product of powder form is packed in the first plastic film        sack, and    -   the first plastic film sack is, at least partly, placed upon the        second plastic film sack,

in which method, in accordance with the invention, such a first plasticfilm sack is provided in which at least a part of the outer surface ofthe flexible wall, the so-called roughened surface-part, comprisesantislip protrusions which antislip protrusions are constituted byroughening particles (preferably granules), of polymer material, fixedto the outer surface and the height, above the outer surface of theplastic film wall, of at least a part of the antislip protrusions isbigger than 12 microns.

The meanings of several words of the invention have already been definedhereinabove. The product of powder form may also comprise particlesbigger than 3 microns; it, however, surely contains particles smallerthan 3 microns, too.

The advantage of the method is that it resists the harmful effect,cumulative in time and spoiling the skidproofing, of the fine dustsettling from the air.

Analogously, it is preferable if in the aforementioned method such afirst plastic film sack is provided in which, in at least one verticalsection taken during a horizontal state of the outer surface, of atleast a part of the antislip protrusions, one or both of the leftmostand rightmost points of the antislip protrusion are at a greater freedistance from the outer surface than 12 microns. The benefit of themethod is that this way a contaminating layer of the extremely finepowder settling can not prevent the engaging fibres from hooking withthe lower, undercut portions of the protrusions.

It is, with respect to skidproofing, preferable if in the aforementionedmethods such a skidproofing material, of a suitable loose fibrousstructure and inherent strength (preferably a nonwoven fabric), isprovided, at least partly placed between the film sacks, which iscapable of a suitable nonslip bond with the antislip protrusions due toits containing the elementary filaments or yarns in such a density andlayer thickness at which a mechanical bond is formed between itselementary filaments or yarns and the antislip protrusions.

Details of this have already been discussed in relation to the abovedescribed, analogous solution.

Analogously, the package mentioned in the previous method is also initself an advantageous invention.

Thus the essence of our respective invention is a package,

-   -   comprising a plastic film sack and a product of powder form        packed therein,    -   the plastic film sack having a flexible wall comprised of a        plastic film,        -   the wall having an outer surface, and    -   the product of powder form comprising, at least partly,        particles smaller than 3 microns,

which package is, in accordance with the invention, such as at least apart of the outer surface of the flexible wall of its plastic film sack,the so-called roughened surface-part, comprises antislip protrusionswhich antislip protrusions are constituted by roughening particles(preferably granules), of polymer material, fixed to the outer surfaceand the height, above the outer surface of the plastic film wall, of atleast a part of the antislip protrusions is bigger than 12 microns.

The advantage of the package is that such a stack can be built therefromas resists the harmful effect, cumulative in time and spoiling theskidproofing, of the fine dust settling from the air.

Analogously, it is preferable if the aforementioned package is such asin at least one vertical section taken during a horizontal state of theouter surface, of at least a part of the antislip protrusions of itsplastic film sack, one or both of the leftmost and rightmost points ofthe antislip protrusion are at a greater free distance from the outersurface than 12 microns. The benefit of such a package is that this waya contaminating layer of the extremely fine powder settling can notprevent the engaging fibres from hooking with the lower, undercutportions of the protrusions.

It is, with respect to skidproofing, preferable if an aforementionedpackage is such as it has a skidproofing material of a suitable loosefibrous structure and inherent strength (preferably a nonwoven fabric),placed suitably to the outer surface of its plastic film sack, which iscapable of a suitable nonslip bond with the antislip protrusions due toits containing the elementary filaments or yarns in such a density andlayer thickness at which a mechanical bond is formed between itselementary filaments or yarns and the antislip protrusions.

A suitable placing and fixing of the skidproofing material, as anengaging element, have already been mentioned hereinabove.

As it has, in the description of the prior art, been mentioned, theharmful quantity of air closed into the bags can, to a certain extent,be decreased with applying perforated packaging films or film sacks,provided with airing orifices. During stacking and the treating, moving,transporting of the sacks, powder gets out, through the airing orificesof the perforated plastic film sacks, to the outside of the sack rightaround the orifices, causing surfacial contamination. In this case, therougher fractions of the product of powder form, otherwise not so easilymixing with the air, can also get out through the orifices. The quantityand fraction size of the powder, seeping out and polluting the outersurface, may typically depend on the way of a successive moving of thecompleted packages or a successive transportation of the completedstacks. The powder of a relatively big size and big quantity, seepingout, behaves similarly to bearing balls and contributes to the slippingup of traditional sack surfaces. We have discovered that underdisadvantageous circumstances the effectiveness of the skidproofing offilm sacks, roughened with antislip protrusions and provided with airingorifices, formed with the engaging element of a fibrous structure will,surprisingly enough, sensitively depend on the size of the granules ofthe aforementioned polluting powder getting to the surface of the sack.If the granules of the polluting powder are too big as compared to theparticles constituting the roughening protrusions then the skidproofingdeteriorates, while with polluting powder granules of a smaller size theskidproofing will be maintained. That may render the skidproofing systemunreliable since it makes the degree of skidproofness depend on the wayof the stacking, for example on to what an extent, during the stackingor a successive transportation, the individual sacks are shaken orcompressed thus how many and how big dust granules are pressed out ofthem through the airing orifices. The reason thereof is certainly thatthe bigger granules can better fill in the space between the antislipprotrusions and thereby they worsen the penetration of the antislipprotrusions between the fibres of the engaging element. Such adistinction can not be experienced in case of traditional (i.e., notroughed) perforated film sacks, as in their case both the rougher andfiner fractions of the dust granules, getting out through the airingorifice and settling directly on the film, make the surface of the sacksslippery, similarly to bearing balls. It is our object to present suchan application of the skidproofing system, consisting of rough andfibrous components, as eliminates the unreliability originating from theaforementioned sensitivity.

The powder, being in the sack and flowing out through the airingorifice, partly fills, and blocks up, the inside of the airing orificethus soon such a state develops in which a hole, much smaller than theairing orifice, is maintained for the granules to flow out through.Thus, in the end, only particles much smaller than the airing orificeflow out from the sack in bigger quantities. We have recognised that ifsuch a sack is applied for packing fine powder whose airing orifices arenot too big as compared to the antislip protrusions then it will helpmaintain the effectiveness of the skidproofing system, comprised ofrough and fibrous components, during the stacking and a successivetransportation. As concerning the disadvantageous effect of a possiblytoo poor airing-out, as a result of the too small airing orifices, itcan be well balanced with the skidproofing system of rough film andengaging element. Thus the essence of our invention is a method fortreating a package, in which

-   -   a first plastic film sack is provided,        -   the first plastic film sack having a flexible wall            comprising a plastic film,            -   the wall having an outer surface, and            -   the wall having at least one airing area comprising                airing orifices, of suitable size and closeness,                penetrating through the wall, and    -   contents of powder form, packed in the first plastic film sack,        are provided, and    -   a second plastic film sack is provided, and    -   the first plastic film sack is, at least partly, placed upon the        second plastic film sack,

in which method, in accordance with the invention, such a first plasticfilm sack is provided in which at least a part of the outer surface ofthe flexible wall, the so-called roughened surface-part, comprisesantislip protrusions which antislip protrusions are constituted byroughening particles (preferably granules), of polymer material, fixedto the outer surface and the height, above the outer surface of theplastic film wall, of at least a part of the antislip protrusions isbigger than one fortieth (preferably one thirtieth, more preferably onetwentieth, even more preferably one tenth) of the size of at least apart of the airing orifices.

The meanings of several words of the invention have already been definedin detail, hereinabove. The sack may have one or more airing areas, ofsuitable size and location, depending on the particular application.There are airing orifices in the airing area, in which the essence isthat they, penetrating through the wall of the sack, are capable ofleading the air out from within the sack. These can be, for example,pinholes pricked with cold or hot pins, or slit openings, or aperturesformed, during the weaving, between the fibres of the woven materialetc. Knowing the particular application, the skilled person can useairing orifices of a suitable size and closeness which let out muchenough of the air but sufficiently retain the contents. The contents ofpowder form are packed into the film sack, i.e., the sack contains thecontents, and the sack is preferably closed but it can be open as well.The contents of powder form may be of any kind suitable for packing in afilm sack. The contents of powder form are preferably constituted by apowder mixed with air. The second plastic film sack can be similar to ordifferent from the first one and it can also be airing.

It is important that the airing orifices should be small enough and of asufficiently low closeness in order that the tearing parameters(primarily e.g., the tear strength) of the flexible wall remain goodenough even in the airing area. The size of the airing orifice is thebiggest extent of the airing orifice taken in a view from a directionnormal to the outer surface. It is, for example, in case of an orificeof circular shape the diameter of the circle. The height of theprotrusion is thus greater than the size of the airing orifice dividedby forty. The advantage of the method is that the skidproofing isreliably maintained therein.

It is, with respect to skidproofing, preferable if in the method such askidproofing material, of a suitable loose fibrous structure andinherent strength (preferably a nonwoven fabric), is provided, at leastpartly placed between the film sacks, which is capable of a suitablenonslip bond with the antislip protrusions due to its containing theelementary filaments or yarns in such a density and layer thickness atwhich a mechanical bond is formed between its elementary filaments oryarns and the antislip protrusions.

Details thereof have already been discussed at the aforementionedanalogous solutions.

It is our object to present a new plastic film sack preferablyapplicable with the aforementioned method, based on the recognitionpresented hereinabove. The essence of our respective invention is aplastic film sack, suitable for the packaging of contents of powderform, comprising

-   -   a flexible wall comprised of a plastic film,        -   the wall having an outer surface,    -   the wall having at least one airing area comprising airing        orifices, of suitable size and closeness, penetrating through        the wall,

the plastic film sack, in accordance with the invention, being such asat least a part of the outer surface of its flexible wall, the so-calledroughened surface-part, comprises antislip protrusions which antislipprotrusions are constituted by roughening particles (preferablygranules), of polymer material, fixed to the outer surface and theheight, above the outer surface of the plastic film wall, of at least apart of the antislip protrusions is bigger than one fortieth (preferablyone thirtieth, more preferably one twentieth, even more preferably onetenth) of the size of at least a part of the airing orifices.

The features of the airing area and airing orifices have already beendiscussed above.

This sack is advantageous because it is suitable for forming such airingstacks in which the skidproofing can reliably be maintained.

With analogy to what has been mentioned above, it is preferable if theplastic film sack is such as in at least one vertical section, takenduring a horizontal state of the outer surface, of at least a part ofits antislip protrusions one or both of the leftmost and rightmostpoints of the antislip protrusion are at a greater free distance fromthe outer surface than one fortieth (preferably one thirtieth, morepreferably one twentieth, even more preferably one tenth) of the size ofat least a part of the airing orifices.

It is, with respect to skidproofing, preferable if an aforementionedplastic film sack is such as it has a skidproofing material of asuitable loose fibrous structure and inherent strength (preferably anonwoven fabric), placed suitably to its outer surface, which is capableof a suitable nonslip bond with the antislip protrusions due to itscontaining the elementary filaments or yarns in such a density and layerthickness at which a mechanical bond is formed between its elementaryfilaments or yarns and the antislip protrusions.

It is our objective to present a new plastic film roll, advantageouslyapplicable for making the sack described above, based on the recognitionpresented above. The essence of our respective invention is a plasticfilm roll, comprising

-   -   a reel    -   a plastic film, suitable for making a packaging sack, wound up        in a longitudinal direction, in several coils around the reel,    -   the plastic film having outer surfaces adjoining the        neighbouring coils,    -   the plastic film having one or more airing areas comprising        airing orifices, of suitable size and closeness, penetrating        through the wall and meeting at least one outer surface,

the plastic film roll, in accordance with the invention, being such asits plastic film has one or more surface parts, the so-called roughenedsurface-parts, that comprise antislip protrusions which antislipprotrusions are constituted by roughening particles (preferablygranules), of polymer material, fixed to the outer surface and theheight, above the outer surface of the-plastic film wall, of at least apart of the antislip protrusions is bigger than one fortieth (preferablyone thirtieth, more preferably one twentieth, even more preferably onetenth) of the size of at least a part of the airing orifices.

The reel may be hollow or solid, its material may be paper, plastic orany other suitable substance. The reel is the core of the roll, the longfilm becomes treatable, portable by being wound up thereon. The reel ismost often a strong paper tube. The longitudinal direction of the rollis perpendicular to the axis of the reel. The plastic film of the filmroll is formed wound up in the longitudinal direction around the reel.The plastic film is suitable for making a packaging sack, i.e., it isthick, strong and weldable enough for the particular application. Theplastic film is wound up around the reel in multiple coils. Thus thefilm roll can be characterised by having been made with winding up along film, in several coils, around a reel. The plastic film can be aflat film, a tube, a tube slit at one side (a so-called half-tube), aside gusseted tube or such a variation of any of these as has beenformed with a folding along longitudinal folding lines, but it can be ofany other suitable form. One coil, as is clear for the skilled person,contains that complete section of the long, single-layer ormultiple-layer film whose length is the circumference of the coil. Allparts of the given section of the long film, for example in case of afilm tube both walls of the given section of the tube, form parts of thesame coil in the film roll. The outer surfaces in the plastic film roll,contacting the neighbouring coils, can be detached from theaforementioned neighbouring coils via unwinding the film, e.g. filmtube, from the roll. On the contrary, however, for example the innersurface of a film tube, laid flat, is in touch with the inner surfaceopposing it and being in the same coil independently from a winding upor an unwinding. In the airing area there are airing orifices leadingout to the outer surface of the film and penetrating through the filmthereby making it possible to let the air out from the sacks, formedlater. Being aware of a particular application, the skilled person willbe able to apply airing orifices of suitable size and closeness that letout much enough air but sufficiently retain the contents. It isimportant that the airing orifices should be small enough and of asufficiently low closeness in order that the tearing parameters(primarily e.g., the tear strength) of the film remain good enough evenin the airing area.

This film roll is advantageous because it is suitable for forming suchairing film sacks with which the skidproofing can reliably be maintainedduring stacking.

With analogy to what has been mentioned above, it is preferable if theaforementioned plastic film roll is such as in at least one verticalsection, taken during a horizontal state of the outer surface, of atleast a part of its antislip protrusions one or both of the leftmost andrightmost points of the antislip protrusion are at a greater freedistance from the outer surface than one fortieth (preferably onethirtieth, more preferably one twentieth, even more preferably onetenth) of the size of at least a part of the airing orifices.

It is, with respect to skidproofing, preferable if an aforementionedplastic film roll is such as it has a skidproofing material of asuitable loose fibrous structure and inherent strength (preferably anonwoven fabric), placed suitably to its outer surface, which is capableof a suitable nonslip bond with the antislip protrusions due to itscontaining the elementary filaments or yarns in such a density and layerthickness at which a mechanical bond is formed between its elementaryfilaments or yarns and the antislip protrusions.

A BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a plastic film roll.

FIG. 2 is an airing orifice in section.

FIG. 3 is the side view of an antislip protrusion with the section ofthe plastic film wall.

FIG. 4 is a perspective view of a plastic film sack.

FIG. 5 is a perspective view of a filled package.

DESCRIPTION OF THE PREFERRED EMBODIMENTS EXAMPLE 1 A Plastic Film Roll(See the Drawings)

The plastic film roll 1 comprises plastic film 3 wound up in alongitudinal direction 19 around a paper reel 2. The plastic film 3 is aside gusseted tube of polyethylene whose wall 18 is 150 microns thick.In an empty, layflat state of the tube the distance between the twoouter edges, being along the side gussets 4, i.e., the width of the tubeis 400 mm's.

The entire outer surface 5 of the plastic film 3 is a roughenedsurface-part 6, and comprises antislip protrusions 7. The latter areconstituted by granules of polyethylene, welded to the outer surface 5.The closeness, in the surface, of the antislip protrusions 7 is 600pieces per 100 square cm's, and the height 8 of the antislip protrusions7 above the outer surface 5 of the plastic film 3 is 240 microns inaverage. In at least one view, taken from a horizontal direction duringa horizontal state of the outer surface 5, of most of the antislipprotrusions 7, both of the leftmost and rightmost points of the antislipprotrusion 7 are at a greater free distance 9 from the outer surface 5than 90 microns.

In one of the main outer surfaces 5, adjoining the neighbouring coils,of the tube-form plastic film 3, at a distance of 55 mm's in eitherdirection from the longitudinal centre line between the side gussets 4,along two, respective, lines parallel with the longitudinal centre linethere are two, respective, lines of airing orifices 10. The airingorifices 10 are round shaped perforations of a size 20, diameter, of 80microns, penetrating through the plastic film 3, meeting the respectiveouter surface 5, located along the aforementioned line at a distance of20 mm's from each other.

There is a nonwoven fabric 12 of a width of 150 mm's, as a skidproofingmaterial 13, adhered, with a continuous filament of adhesive material,to the outer surface 5, including the airing area 11, of the plasticfilm 3. The nonwoven fabric 12 has a surface weight of 14 g/m² and has agreat inherent strength, tear strength. The nonwoven fabric 12 is of asufficiently loose fibrous structure and contains the infinitepolypropylene elementary filaments in such a density and layer thicknessthat between its elementary filaments and the antislip protrusions 7 amechanical bond, withstanding a very strong shearing load, is formed.The antislip protrusions 7 are suitable for an appropriate antislipengagement with the nonwoven fabric 12 due to their being of a size andshape, suitable for penetrating between the elementary filaments of thenonwoven fabric 12 to such an extent that a mechanical bond is createdbetween the elementary filaments and the antislip protrusions 7.

EXAMPLE 2 A Plastic Film Sack (See the Drawings)

The plastic film sack 14 is a side gusseted sack of a height of 900mm's, made from the tube of plastic film 3 of Example 1, with acrosswise-cutting and welding thereof.

EXAMPLE 3 A Method for Treating a Package (See the Drawings)

As a first plastic film sack 14 such a plastic film sack 14 is providedwhich is identical with the plastic film sack 14 described in Example 2and which has a lower main abutting surface 15, laid on which the filledplastic film sack 14 can be stored, and an opposing, upper main abuttingsurface 15 including the airing area 11. The nonwoven fabric 12 formingthe skidproofing material 13 is fixed to the upper main abutting surface15. A second plastic film sack 14, identical in parameters with thefirst plastic film sack 14, is provided. As a product of powder form 16,a mixture of cement and fine sand, a so-called dry-mix concrete powder,is provided, the particle size of 1 mass-percent of which is smallerthan 1 micron and the particle size of 1 mass-percent of which is biggerthan 2100 microns, and is packed into the plastic film sacks 14. One ofthe, reliably skidproof, packages 17 formed thereby is placed upon theother, either in a columnar way or with an overlap. Meanwhile, theirupper main abutting surfaces 15 are kept turned upwards.

EXAMPLE 4 A Method for Treating a Package

The method differs from that of Example 3 in that unperforated plasticfilm sacks, free of airing orifices, are applied.

EXAMPLE 5 A Method for Treating a Package

The method differs from that of Example 4 in that plastic film sacksfree of an adhered-on nonwoven fabric are applied, whose entire outersurface is roughened with antislip protrusions, and a stick-sheet,comprising a nonwoven fabric of a surface weight of 35 g/m², is placedbetween the packages put on top of each other. The nonwoven fabric is ofa sufficiently loose fibrous structure and contains the infinitepolypropylene elementary filaments in such a density and layer thicknessthat between its elementary filaments and the antislip protrusions amechanical bond, withstanding a very strong shearing load, is formed.

INDEX OF SIGNS OF THE FIGURES

-   1 plastic film roll-   2 reel-   3 plastic film-   4 side gusset-   5 outer surface-   6 roughened surface-part-   7 antislip protrusion-   8 height of antislip protrusion above the outer surface-   9 free distance-   10 airing orifice-   11 airing area-   12 nonwoven fabric-   13 skidproofing material-   14 plastic film sack-   15 main abutting surface of plastic film sack-   16 product of powder form-   17 package-   18 wall-   19 longitudinal direction-   20 size of airing orifice

1-51. (canceled)
 52. A method for treating a package, in which a firstplastic film sack is provided, the first plastic film sack having aflexible wall comprising a plastic film, the wall having an outersurface, a second plastic film sack is provided, and a product of powderform is provided that has an upper size limit wherein the particle sizeof 1 mass-percent of the particles of the product of powder form isbigger than the upper size limit the upper size limit being at most 5000microns, and a lower size limit wherein the particle size of 1mass-percent of the particles of the product of powder form is smallerthan the lower size limit, the product of powder form is packed in thefirst plastic film sack, and the first plastic film sack is, at leastpartly, placed upon the second plastic film sack, characterised in thatsuch a first plastic film sack is provided in which at least a part ofthe outer surface, the roughened surface-part, comprises antislipprotrusions which antislip protrusions are constituted by granules, orother essentially point-like particles of polymer material, fixed to theouter surface and at least some of the antislip protrusions are undercutwhose projection to the outer surface is bigger than their intersectionwith the outer surface and in at least one vertical section, takenduring a horizontal state of the outer surface, of at least some of theundercut antislip protrusions one or both of the leftmost and rightmostpoints of the antislip protrusion are at a greater free distance fromthe outer surface than the lower size limit of the product of powderform.
 53. The method according to claim 52, wherein such a first plasticfilm sack is provided in which, in all vertical sections taken during ahorizontal state of the outer surface, of at least some of the undercutantislip protrusions, one or both of the leftmost and rightmost pointsof the antislip protrusion are at a greater free distance from the outersurface than the lower size limit of the product of powder form.
 54. Themethod according to claim 53, wherein such a skidproofing material, of asuitable loose fibrous structure and inherent strength, is provided, atleast partly placed between the film sacks, which is capable of asuitable nonslip bond with the antislip protrusions due to itscontaining the elementary filaments or yarns in such a density and layerthickness at which a mechanical bond is formed between its elementaryfilaments or yarns and the antislip protrusions.
 55. The methodaccording to claim 52, wherein such a skidproofing material, of asuitable loose fibrous structure and inherent strength, is provided, atleast partly placed between the film sacks, which is capable of asuitable nonslip bond with the antislip protrusions due to itscontaining the elementary filaments or yarns in such a density and layerthickness at which a mechanical bond is formed between its elementaryfilaments or yarns and the antislip protrusions.
 56. A package (17),comprising a plastic film sack (14) and a product of powder form (16)packed therein, the plastic film sack (14) having a flexible wall (18)comprised of a plastic film (3), the wall (18) having an outer surface(5), and the product of powder form (16) having an upper size limitwherein the particle size of 1 mass-percent of the particles of theproduct of powder form (16) is bigger than the upper size limit, theupper size limit being at most 5000 microns, and a lower size limitwherein the particle size of 1 mass-percent of the particles of theproduct of powder form (16) is smaller than the lower size limit,characterised in that at least a part of the outer surface (5), theroughened surface-part (6), comprises antislip protrusions (7) whichantislip protrusions (7) are constituted by granules, or otheressentially point-like particles of polymer material, fixed to the outersurface (5) and at least some of the antislip protrusions (7) areundercut whose projection to the outer surface (5) is bigger than theirintersection with the outer surface (5) and in at least one verticalsection, taken during a horizontal state of the outer surface (5), of atleast some of the undercut antislip protrusions (7) one or both of theleftmost and rightmost points of the antislip protrusion (7) are at agreater free distance (9) from the outer surface (5) than the lower sizelimit of the product of powder form (16).
 57. The package (17) accordingto claim 56, wherein in all vertical sections, taken during a horizontalstate of the outer surface (5), of at least some of the undercutantislip protrusions (7), one or both of the leftmost and rightmostpoints of the antislip protrusion (7) are at a greater free distance (9)from the outer surface (5) than the lower size limit of the product ofpowder form (16).
 58. The package (17) according to claim 57, wherein ithas a skidproofing material (13) of a suitable loose fibrous structureand inherent strength, placed suitably to the outer surface (5) of itsplastic film sack (14), which is capable of a suitable nonslip bond withthe antislip protrusions (7) due to its containing the elementaryfilaments or yarns in such a density and layer thickness at which amechanical bond is formed between its elementary filaments or yarns andthe antislip protrusions (7).
 59. The package (17) according to claim56, wherein it has a skidproofing material (13) of a suitable loosefibrous structure and inherent strength, placed suitably to the outersurface (5) of its plastic film sack (14), which is capable of asuitable nonslip bond with the antislip protrusions (7) due to itscontaining the elementary filaments or yarns in such a density and layerthickness at which a mechanical bond is formed between its elementaryfilaments or yarns and the antislip protrusions (7).
 60. A method fortreating a package, in which a first plastic film sack is provided, thefirst plastic film sack having a flexible wall comprising a plasticfilm, the wall having an outer surface, a second plastic film sack isprovided, and a product of powder form is provided that comprises, atleast partly, particles of a size smaller than 3 microns, the product ofpowder form is packed in the first plastic film sack, and the firstplastic film sack is, at least partly, placed upon the second plasticfilm sack, characterised in that such a first plastic film sack isprovided in which at least a part of the outer surface, the roughenedsurface-part, comprises antislip protrusions which antislip protrusionsare constituted by granules, or other essentially point-like particlesof polymer material, fixed to the outer surface and at least some of theantislip protrusions are undercut and in at least one vertical section,taken during a horizontal state of the outer surface, of at least someundercut antislip protrusions one or both of the leftmost and rightmostpoints of the antislip protrusion are at a greater free distance fromthe outer surface than 12 microns.
 61. The method according to claim 60,wherein such a first plastic film sack is provided in which, in allvertical sections taken during a horizontal state of the outer surface,of at least some undercut antislip protrusions, one or both of theleftmost and rightmost points of the antislip protrusion are at agreater free distance from the outer surface than 12 microns.
 62. Themethod according to claim 61, wherein such a skidproofing material, of asuitable loose fibrous structure and inherent strength, is provided, atleast partly placed between the film sacks, which is capable of asuitable nonslip bond with the antislip protrusions due to itscontaining the elementary filaments or yarns in such a density and layerthickness at which a mechanical bond is formed between its elementaryfilaments or yarns and the antislip protrusions.
 63. The methodaccording to claim 60, wherein such a skidproofing material, of asuitable loose fibrous structure and inherent strength, is provided, atleast partly placed between the film sacks, which is capable of asuitable nonslip bond with the antislip protrusions due to itscontaining the elementary filaments or yarns in such a density and layerthickness at which a mechanical bond is formed between its elementaryfilaments or yarns and the antislip protrusions.
 65. A package (17),comprising a plastic film sack (14) and a product of powder form (16)packed therein, the plastic film sack (14) having a flexible wall (18)comprised of a plastic film (3), the wall (18) having an outer surface(5), and the product of powder form (16) comprising, at least partly,particles of a size smaller than 3 microns, characterised in that atleast a part of the outer surface (5), the roughened surface-part (6),comprises antislip protrusions (7) which antislip protrusions (7) areconstituted by granules, or other essentially point-like particles ofpolymer material, fixed to the outer surface (5) and at least some ofthe antislip protrusions (7) are undercut and in at least one verticalsection, taken during a horizontal state of the outer surface (5), of atleast some undercut antislip protrusions (7) one or both of the leftmostand rightmost points of the antislip protrusion (7) are at a greaterfree distance (9) from the outer surface (5) than 12 microns.
 66. Thepackage (17) according to claim 65, wherein in all vertical sectionstaken during a horizontal state of the outer surface (5), of at leastsome undercut antislip protrusions (7), one or both of the leftmost andrightmost points of the antislip protrusion (7) are at a greater freedistance (9) from the outer surface (5) than 12 microns.
 67. The package(17) according to claim 66, wherein it has a skidproofing material (13)of a suitable loose fibrous structure and inherent strength, placedsuitably to the outer surface (5) of its plastic film sack (14), whichis capable of a suitable nonslip bond with the antislip protrusions (7)due to its containing the elementary filaments or yarns in such adensity and layer thickness at which a mechanical bond is formed betweenits elementary filaments or yarns and the antislip protrusions (7). 68.The package (17) according to claim 65, wherein it has a skidproofingmaterial (13) of a suitable loose fibrous structure and inherentstrength, placed suitably to the outer surface (5) of its plastic filmsack (14), which is capable of a suitable nonslip bond with the antislipprotrusions (7) due to its containing the elementary filaments or yarnsin such a density and layer thickness at which a mechanical bond isformed between its elementary filaments or yarns and the antislipprotrusions (7).
 69. A method for treating a package, in which a firstplastic film sack is provided, the first plastic film sack having aflexible wall comprising a plastic film, the wall having an outersurface, and the wall having at least one airing area comprising airingorifices, of suitable size and closeness, penetrating through the wall,and contents of powder form, packed in the first plastic film sack, areprovided, and a second plastic film sack is provided, and the firstplastic film sack is, at least partly, placed upon the second plasticfilm sack, characterised in that such a first plastic film sack isprovided in which at least a part of the outer surface, the roughenedsurface-part, comprises antislip protrusions, which antislip protrusionsare constituted by granules, or other essentially point-like particlesof polymer material, fixed to the outer surface and at least some of theantislip protrusions are undercut and in at least one vertical section,taken during a horizontal state of the outer surface, of at least someundercut antislip protrusions one or both of the leftmost and rightmostpoints of the antislip protrusion are at a greater free distance fromthe outer surface than one fortieth of the size of at least some airingorifices.
 70. The method according to claim 69, wherein such a firstplastic film sack is provided in which in all vertical sections, takenduring a horizontal state of the outer surface, of at least someundercut antislip protrusions one or both of the leftmost and rightmostpoints of the antislip protrusion are at a greater free distance fromthe outer surface than one fortieth of the size of at least some airingorifices.
 71. The method according to claim 69, wherein in at least onevertical section, taken during a horizontal state of the outer surface,of at least some undercut antislip protrusions one or both of theleftmost and rightmost points of the antislip protrusion are at agreater free distance from the outer surface than one tenth of the sizeof at least some airing orifices.
 72. The method according to claim 71,wherein in all vertical sections, taken during a horizontal state of theouter surface, of at least some undercut antislip protrusions one orboth of the leftmost and rightmost points of the antislip protrusion areat a greater free distance from the outer surface than one tenth of thesize of at least some airing orifices.
 73. The method according to claim72, wherein such a skidproofing material, of a suitable loose fibrousstructure and inherent strength, is provided, at least partly placedbetween the film sacks, which is capable of a suitable nonslip bond withthe antislip protrusions due to its containing the elementary filamentsor yarns in such a density and layer thickness at which a mechanicalbond is formed between its elementary filaments or yarns and theantislip protrusions.
 74. The method according to claim 69, wherein sucha skidproofing material, of a suitable loose fibrous structure andinherent strength, is provided, at least partly placed between the filmsacks, which is capable of a suitable nonslip bond with the antislipprotrusions due to its containing the elementary filaments or yarns insuch a density and layer thickness at which a mechanical bond is formedbetween its elementary filaments or yarns and the antislip protrusions.75. The method according to claim 70, wherein such a skidproofingmaterial, of a suitable loose fibrous structure and inherent strength,is provided, at least partly placed between the film sacks, which iscapable of a suitable nonslip bond with the antislip protrusions due toits containing the elementary filaments or yarns in such a density andlayer thickness at which a mechanical bond is formed between itselementary filaments or yarns and the antislip protrusions.
 76. Themethod according to claim 71, wherein such a skidproofing material, of asuitable loose fibrous structure and inherent strength, is provided, atleast partly placed between the film sacks, which is capable of asuitable nonslip bond with the antislip protrusions due to itscontaining the elementary filaments or yarns in such a density and layerthickness at which a mechanical bond is formed between its elementaryfilaments or yarns and the antislip protrusions.
 77. A plastic film sack(14), suitable for the packaging of a product of powder form (16),comprising a flexible wall (18) comprised of a plastic film (3), thewall (18) having an outer surface (5), the wall (18) having at least oneairing area (11) comprising airing orifices (10), of suitable size andcloseness, penetrating through the wall (18), characterised in that atleast a part of the outer surface (5), the roughened surface-part (6),comprises antislip protrusions (7) which antislip protrusions (7) areconstituted by granules, or other essentially point-like particles ofpolymer material, fixed to the outer surface (5) and at least some ofthe antislip protrusions (7) are undercut and in at least one verticalsection, taken during a horizontal state of the outer surface (5), of atleast some undercut antislip protrusions (7) one or both of the leftmostand rightmost points of the antislip protrusion (7) are at a greaterfree distance (9) from the outer surface (5) than one fortieth of thesize (20) of at least some airing orifices (10).
 78. The plastic filmsack (14) according to claim 77, wherein in all vertical sections, takenduring a horizontal state of the outer surface (5), of at least someundercut antislip protrusions (7) one or both of the leftmost andrightmost points of the antislip protrusion (7) are at a greater freedistance (9) from the outer surface (5) than one fortieth of the size(20) of at least some airing orifices (10).
 79. The plastic film sack(14) according to claim 77, wherein in at least one vertical section,taken during a horizontal state of the outer surface (5), of at leastsome undercut antislip protrusions (7) one or both of the leftmost andrightmost points of the antislip protrusion (7) are at a greater freedistance (9) from the outer surface (5) than one tenth of the size (20)of at least some airing orifices (10).
 80. The plastic film sack (14)according to claim 79, wherein in all vertical sections, taken during ahorizontal state of the outer surface (5), of at least some undercutantislip protrusions (7) one or both of the leftmost and rightmostpoints of the antislip protrusion (7) are at a greater free distance (9)from the outer surface (5) than one tenth of the size (20) of at leastsome airing orifices (10).
 81. The plastic film sack (14) according toclaim 80, wherein it has a skidproofing material (13) of a suitableloose fibrous structure and inherent strength, placed suitably to itsouter surface (5), which is capable of a suitable nonslip bond with theantislip protrusions (7) due to its containing the elementary filamentsor yarns in such a density and layer thickness at which a mechanicalbond is formed between its elementary filaments or yarns and theantislip protrusions (7).
 82. The plastic film sack (14) according toclaim 77, wherein it has a skidproofing material (13) of a suitableloose fibrous structure and inherent strength, placed suitably to itsouter surface (5), which is capable of a suitable nonslip bond with theantislip protrusions (7) due to its containing the elementary filamentsor yarns in such a density and layer thickness at which a mechanicalbond is formed between its elementary filaments or yarns and theantislip protrusions (7).
 83. The plastic film sack (14) according toclaim 78, wherein it has a skidproofing material (13) of a suitableloose fibrous structure and inherent strength, placed suitably to itsouter surface (5), which is capable of a suitable nonslip bond with theantislip protrusions (7) due to its containing the elementary filamentsor yarns in such a density and layer thickness at which a mechanicalbond is formed between its elementary filaments or yarns and theantislip protrusions (7).
 84. The plastic film sack (14) according toclaim 79, wherein it has a skidproofing material (13) of a suitableloose fibrous structure and inherent strength, placed suitably to itsouter surface (5), which is capable of a suitable nonslip bond with theantislip protrusions (7) due to its containing the elementary filamentsor yarns in such a density and layer thickness at which a mechanicalbond is formed between its elementary filaments or yarns and theantislip protrusions (7).
 85. A plastic film roll (1), comprising a reel(2) and a plastic film (3), suitable for making a-packaging sack, woundup in a longitudinal direction (19), in several coils around the reel(2), the plastic film (3) having outer surfaces (5) adjoining theneighbouring coils, the plastic film (3) having one or more airing areas(11) comprising airing orifices (10), of suitable size (20) andcloseness, penetrating through the plastic film (3) and meeting at leastone outer surface (5), characterised in that its plastic film (3) hasone or more surface parts, the roughened surface-parts (6), thatcomprise antislip protrusions (7) which antislip protrusions (7) areconstituted by granules, or other essentially point-like particles ofpolymer material, fixed to the outer surface (5) and at least some ofthe antislip protrusions (7) are undercut and in at least one verticalsection, taken during a horizontal state of the outer surface (5), of atleast some undercut antislip protrusions (7) one or both of the leftmostand rightmost points of the antislip protrusion (7) are at a greaterfree distance (9) from the outer surface (5) than one fortieth of thesize (20) of at least some airing orifices (10).
 86. The plastic filmroll (1) according to claim 85, wherein in all vertical sections, takenduring a horizontal state of the outer surface (5), of at least someundercut antislip protrusions (7) one or both of the leftmost andrightmost points of the antislip protrusion (7) are at a greater freedistance (9) from the outer surface (5) than one fortieth of the size(20) of at least some airing orifices (10).
 87. The plastic film roll(1) according to claim 85, wherein in at least one vertical section,taken during a horizontal state of the outer surface (5), of at leastsome undercut antislip protrusions (7) one or both of the leftmost andrightmost points of the antislip protrusion (7) are at a greater freedistance (9) from the outer surface (5) than one tenth of the size (20)of at least some airing orifices (10).
 88. The plastic film roll (1)according to claim 87, wherein in all vertical sections, taken during ahorizontal state of the outer surface (5), of at least some undercutantislip protrusions (7) one or both of the leftmost and rightmostpoints of the antislip protrusion (7) are at a greater free distance (9)from the outer surface (5) than one tenth of the size (20) of at leastsome airing orifices (10).
 89. The plastic film roll (1) according toclaim 88, wherein it has a skidproofing material (13) of a suitableloose fibrous structure and inherent strength, placed suitably to itsouter surface (5), which is capable of a suitable nonslip bond with theantislip protrusions (7) due to its containing the elementary filamentsor yarns in such a density and layer thickness at which a mechanicalbond is formed between its elementary filaments or yarns and theantislip protrusions (7).
 90. The plastic film roll (1) according toclaim 85, wherein it has a skidproofing material (13) of a suitableloose fibrous structure and inherent strength, placed suitably to itsouter surface (5), which is capable of a suitable nonslip bond with theantislip protrusions (7) due to its containing the elementary filamentsor yarns in such a density and layer thickness at which a mechanicalbond is formed between its elementary filaments or yarns and theantislip protrusions (7).
 91. The plastic film roll (1) according toclaim 86, wherein it has a skidproofing material (13) of a suitableloose fibrous structure and inherent strength, placed suitably to itsouter surface (5), which is capable of a suitable nonslip bond with theantislip protrusions (7) due to its containing the elementary filamentsor yarns in such a density and layer thickness at which a mechanicalbond is formed between its elementary filaments or yarns and theantislip protrusions (7).
 92. The plastic film roll (1) according toclaim 87, wherein it has a skidproofing material (13) of a suitableloose fibrous structure and inherent strength, placed suitably to itsouter surface (5), which is capable of a suitable nonslip bond with theantislip protrusions (7) due to its containing the elementary filamentsor yarns in such a density and layer thickness at which a mechanicalbond is formed between its elementary filaments or yarns and theantislip protrusions (7).